難揮発生カルボン酸の定量
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概要
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Determination of slightly volatile carboxylic acids such as benzoic, gallic, meta toluic, stearic and lauric acid was carried out by a reaction gas chromatography which involved the formation reaction of the amine-car-boxylic acid salts. The present method is characterized by developing the quantitative aspect of the reaction gas chromatography, so that it has some advantage that it can be carried out by a simpler equipment and procedure, a smaller amount of the sample, and a lower operating temperature than the conventional techniques such as pyrolysis and esterification followed by gas chromatographic analysis.<BR>The procedures of introducing the sample to the reaction column were the same as were reported in the previous paper. Gas chromatographic conditions were: column packing; 10% KOH, 5% Apiezon L coated on acid washed and DMCS-MeOH treated Chromosorb W (60/80), carrier gas flow rate; N<SUB>2</SUB>, 30 m<I>l</I>/min, detector; F. I. D., injection port temperature; 200°C, the temperature of column oven in which the analytical and reaction columns were attached was 64 or 88°C.<BR><I>n</I>-Hexylamine was injected into the sample chamber of gas chromatograph and it reacted with the sample acid in the course of passing through the reaction column. The amine-carboxylic acid salt, the reaction product, and unreacted carboxylic acid remained in the reaction column during the course of whole GC procedures. Repeated injection of <I>n</I>-hexylamine caused stepwise reactions, so that the chromatogram obtained showed the peak of excess <I>n</I>-hexylamine after the completion of the reaction, while no peak appeared before the completion of the reaction.<BR>The amount of sample acid was calculated from the equivalent amount of amine which was determined by subtracting the excess amount of amine from the total amount of amine. Variation of analytical conditions such as the carrier gas flow rate, the amount and the concentration of sample acid and the volume of <I>n</I>-hexylamine injected at one time did not change the recovery of sample. The resulting recovery under the best conditions was about 100%, standard deviation 2.22.8%, and the sample taken was 0.30.2 mg.
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